# The Law of Cosines: What is this about?

A Mathematical Droodle

What if applet does not run? |

The applet could serve to demonstrate the Law of Cosines and also the fact that the centers of the squares constructed (externally) on the sides of a parallelogram form a square, which is known as one of V. Thebault's theorems.

### References

- R. Nelsen,
*Proofs Without Words*, MAA, 1993, p. 19

- The Law of Cosines (Cosine Rule)
- The Illustrated Law of Cosines
- The Law of Sines and Cosines
- The Law of Cosines: Plane Tessellation
- The Law of Cosines: after Thâbit ibn Qurra
- The Law of Cosines: Unfolded Version
- The Law of Cosines (Independent of the Pythagorean Theorem)
- The Cosine Law by Similarity
- The Law of Cosines by Larry Hoehn
- The Law of Cosines - Another PWW
- The Law of Cosines - Yet Another PWW
- Law of Cosines by Ancient Sliding
- The Cosine Law: PWW by S. Kung

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